1. Field
One embodiment of the invention relates to a technology for increasing resolution of an image.
2. Description of the Related Art
Recent progress in the integration of a personal computer (PC) and a television provides more opportunities to view various types of videos (e.g., sport programs such as football, cartoon programs, and movie programs) on a high-resolution display with high definition (HD) exceeding standard definition (SD).
Video broadcast for SD televisions, video recorded on DVD, or the like has low resolution. Therefore, when users view video in HD size (especially, in full HD size, i.e., full HD resolution of 1920×1080 pixels), the resolution of the video is increased. To increase the resolution of an image, technologies, such as linear interpolation and cubic covolution interpolation, have been used to interpolate the pixel value of the image. With these technologies, however, a sharp image cannot be obtained.
In view of this, a super resolution technology has been studied, in which an image is expanded, and high-frequency component pixels are interpolated between pixels of the expanded image to obtain a sharp high-resolution image (see, for example, Japanese Patent Application Publication (KOKAI) Nos. 2008-067110 and 2008-146190). The conventional super resolution technology enhances the sharpness of video, and thus users can enjoy the sharp and clear video.
When an image is sharpened by the super resolution technology, it is sometimes the case that block noise occurs in the image or there are distortions or imperfections in perspective between foreground and background objects in the image.
Besides, image sharpening has been known in which the edge of an image is enhanced to sharpen the appearance of the image. The super resolution technology is completely different from the image sharpening in that high-frequency component pixels are newly created. Therefore, it is difficult to adjust the level of sharpening in the same manner as in the image sharpening.